Russian President Vladimir Putin has signed a law prohibiting the use of Internet proxy services -- including virtual private networks, or VPNs.

The law, signed by Putin on July 29 and published by the government on July 30, was promoted by lawmakers who said it is needed to prevent the spread of extremist material and ideas.

Critics say Putin's government often uses that justification to suppress political dissent.

Almost all of the changes under the law are set to take effect November 1, months ahead of a March 2018 presidential election in which Putin is widely expected to seek and win a new six-year term.

Under the law, Internet providers will be ordered to block websites that offer VPNs and other proxy services. Russians frequently use such websites to access blocked content by routing connections through servers abroad.

Russian authorities in recent years have escalated efforts to prosecute Internet users for online content deemed extremist or insulting to religious believers.